1. Brownian Computation
Charles H. Bennett
IBM Research

2. I. Classification of Computers from thermodynamic viewpoint
A. Irreversible
B. Reversible
1.Ballistic (e.g. billiard ball model )
2. Brownian (e.g. RNA polymerase)
3. Intermediate (like walk on a 1d lattice with
mean free path >1)
II. Error and Error Correction in Brownian Computers

5. Turing machine, illustrating logical irreversibility

6. Kinds of computation graph for Brownian computers
Extraneous predecessors
Forward direction of
Intended computation

7. Potential Energy Surface for Brownian ComputerEe E0
Extraneous (error) state
Initial state
Intended successor
Error probability per step approx. exp [ (E0 -Ee ) / kT ]

8. Proofreading in DNA Replication
Polymerase (1) tries to insert correct base, but occasionally (2) makes an error. Exonuclease (3) tries to remove errors, but occasionally (4) removes correct bases. When both reactions are driven hard forward the error rate is the product of their individual error rates.